Synergistic grease structure modifiers

ABSTRACT

IN A LUBRICATING GREASE COMPRISING A LUBRICATING OIL AND A LITHIUM SOAP OF A C18 HYDROXY FATTY ACID, THE IMPROVEMENT OF USING A SYNERGISTIC COMBINATION OF A LEAST TWO DIFFERENT C2-C10 ALIPHATIC POLYOLS FOR STRUCTURAL MODIFICATION.

United States Patent 3,658,704 SYNERGISTIC GREASE STRUCTURE MODIFIERS George G. Curtis, Westfield, N.J., assignor to Esso Research and Engineering Company No Drawing. Filed June 5, 1969, Ser. No. 830,846 Int. Cl. Cltlm /14 U.S. Cl. 252-42 8 Claims ABSTRACT OF THE DISCLOSURE In a lubricating grease comprising a lubricating oil and a lithium soap of a C hydroxy fatty acid, the improvement of using a synergistic combination of at least two different C2-C10 aliphatic polyols for structural modification.

BACKGROUND OF THE INVENTION Field of the invention This invention is directed to the improvement in lubricating grease compositions comprising a base lubricating oil and a lithium soap of a C hydroxy fatty acid, of using a synergistic combination of at least two different C -C aliphatic polyols for structural modification.

More particularly it is directed to the use, in greases containing a lithium soap of a C hydroxy fatty acid as a thickening agent, of a combination of at least two different aliphatic hydrocarbons, branched or straight chain, polyols consisting of carbon, hydrogen and oxygen and having 2 to carbon atoms and 2 to 8 hydroxy groups per polyol in place of the individual hydroxyl substituted structural modifiers disclosed in the prior art.

Description of the prior art U.S. Pat. 3,158,574 discloses that grease containing lithium hydroxy soaps as a gelling agent, having an improved structure, may be obtained by incorporating a glyceride in the constituents from which the acid constituents of the grease forming soap is derived. During manufacture the glyceride hydrolizes resulting in a glycerol content of about 1.4 wt. percent based on the total composition which acts as a modifier. This patent further teaches that improved properties can also be obtained by the addition of an aliphatic polyhydroxy structure modifying agent. Among the aliphatic structure modifiers taught in said patent are glycols, polyglycols and partial esters of glycols in proportions of between 1% and 4% by wt. based on the total composition.

SUMMARY OF THE INVENTION It has now been discovered that the lubricating properties of hydroxy stearic acid soap greases such as those of said U.S. 3,158,574 can be even further improved by the addition of a combination of at least two dilferent C -C aliphatic polyols as structural modifiers.

More specifically it has now been found that a combination of at least two of these modifying agents exert a synergistic improvement in structural stability and product yield over that obtainable with the use of a single modifier. In addition combinations of modifiers herein proposed generally produce a better grease having better shear and structural stability while requiring less modifier than the similar hydroxy soap grease systems employing a single modifier.

The combination of compounds contemplated for use in this invention are nonaromatic preferably saturated hydroxy materials of about 2 to 10 carbon atoms, preferably 3 to 6 carbon atoms and having 2 to 8, preferably 2 to 6 hydroxy groups. Such compounds include C C alicyclic polyols, and C -C acyclic polyols.

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Among the alicyclic compounds contemplated for use in this invention are 1,2-cyclopentanediol, 1,4-cyclohexanediol and 1,4-bis (hydroxymethyl) cyclohexane.

Preferred for use in this invention are combinations of C to C acyclic polyols. Especially preferred are the C to C acyclic polyols such as 1,2,3-propanetriol, 2- methyl, 2,4-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, 1,2,3,4,5,6-hexanehexol, etc. Most preferred is a combination of sorbitol (which is 1,2,3,4,5,6-hexanehexol) and 1,6-hexanediol.

The weight percent of said combination of modifiers contemplated for use by this invention ranges from about 0.01 to 2% and, preferably, from 0.1 to 1% by weight based on the weight of the total grease composition.

While this invention contemplates the use of a combination of two or more modifiers, preferred is the use of a combination of two modifiers. The relative molar ratios of the two modifiers to each other range from about 1 to 4 to about 4 to 1, preferably 2 to 1 to about 1 to 2. Most preferred is a combination of about equal molar amounts of modifiers.

The methods by which the greases employing the inventive synergistic modifiers are to be manufactured are known in the art. For example, see U.S. 3,158,574. However, contrary to the teachings of U.S. 3,158,574 when using this combination of modifying agents it is no longer necessary to add them at a particular stage of grease manufacture and these modifiers can be added at any time before the grease begins to cool. However, the modifiers are especially effective when most of the cut back oil is slowly added to the concentrated soap base while the temperature is maintained near the maximum manufacturing temperature.

The lubricating oil employed to produce lubricating grease compositions may be conventional grease-making mineral lubricating oils which are well-known in the art.

The hydroxy fatty acids used in forming the thickening agent for the grease is preferably a hydroxy stearic acid with l to 2 hydroxy groups such as 9-hydroxy stearic, IO-hydroxy stearic, 12-hydroxy stearic and 9,10-dihydroxy stearic acid, etc.

The total thickener content should range from about 3 to about 25 wt. percent and preferably 6-12 wt. percent of the total grease composition.

The nature of this invention will be further understood when reference is made to the following examples which include preferred embodiments which are not to be construed as a limitation of the invention.

EXAMPLE 1 562 grams of 12-hydroxy stearic acid and 1500 grams of mineral lubricating oil having a V1. of and a viscosity of 700-775 SUS at F. (hereinafter referred to as Oil A) were added to a laboratory grease kettle and were mixed at F. Then 88.5 grams of lithium hydroxide (LiOH) were added and the heat was raised to 200 F. and held for one hour. The heat was then raised to 340 F. and 8 grams of sorbitol and 8 grams of 1,6-hexanediol were added. The temperature was then further raised to 380 F. and held for 1 hour. 1000 grams of the resulting mixture were then placed in a Hobart mixer and 2050 grams additional Oil A were added to cut back said mixture to a No. 1 grade grease.

EXAMPLE 2 562 grams of 12-hydroxy stearic acid and 1500 grams of Oil A were added to a laboratory grease kettle and were mixed at 160 F. 88.5 grams of lithium hydroxide were then added and the heat was raised to 200 F. and held for 1 hour. The heat was then raised to 340 F. and

8 grams of sorbitol and 8 grams of 1,6-hexanediol predissolved in 100 grams of Oil A were added. The temperature was then further raised to 380 F. and held for 1 hour. 1000 grams of the resulting mixture were then 4 sists of an outer steel cylinder 182 millimeters in length and 90 millimeters in inside diameter. This cylinder is permanently closed at one end while the other end is provided with a flange and a removable cover plate. An inner cylindrical roller 177 millimeters in length and 60 placed in a Hobart mixer and 2010 grams of additional 5 Oil A were added to cut back said mixture to a No. 1 millimeters in outside diameter is filled with lead to give grade a weight of about 11 lbs. The outer cylinder has a wall thickness of 3 millimeters, and the same thickness of steel Comparatlvc Grease A Efiect Pexanedlol alonc is soldered on each end of the inner cylinder so that no 0? grams of Y Y steaflcoacld, 1500 grams of lead is exposed. The operation of this test equipment 0 f 1fig hggsxige ggg gdzgg gixi g? f 'gfi f (3012181183 of placlingd a we1ghted antilpunt lcif lubficatmghgreasle a in e open cy in er, inserting e r0 er cosing e cyiifi 'r iifi giii ii rzisssitzrtrsuizrsz is; rer: t 4 i.

r een o s r10 e es sam elsremove an temperature 'was then increased to 390 F. and this tem- 15 t t d b means f miniature penetrgmeter cone to d Peratum was p constant one hour- 1000 grams of termine any change in consistency. The figures in Table the resulting mixture were then placed in the Hobart 1 represent h percentage f change and 2500 grams addltlonal A were added- Table I demonstrates the results of modifier synergism EXAMPLE 3 i2n grgaes. Whil: theGgreaseskfgrmed ltiiigmples 1 and an ompara 1V6 rease ave a on e same cong giams of fi gi g and and i g g sistency, started off with the same relative proportions o d f a e o a a grease e an of starting materials and have about the same total mod- E 3g 3 j g? f ifier content, the synergistic combinations in Examples f I? h Th P tfi ih l b g and 2 exhibited far more stability than the single modg g A :2 :5 ggg g S 2 ifier in Comparative Grease A. The tests run or Comparah Xan d f gr dd d tive Greases B and C and the grease of Example 3 simii i th f t r855; i 8 larly demonstrate the synergism which occurs at even 2 5 :2 22? .?1 g g 1 a1 H Ha th lower concentrations. Furthermore, the poor results shown imine (ari antioxiilant wer 351 'I 'he r iiixtur w as by Comparatwe {eases B-and c-l-nghhghts the allowed to cool overnight 220 grams of the resulting fi i of g.g stabllity from a combma' mixture were then combined with 480 grams of Oil A to Hon 0 t ese ow mo 1 at concentrations produce the finished grease. EXAMPLE 4 Comparative Grease B-Efiect of 1,6-hexanediol grams of y y Stearic acid and 0 grams The procedure and materials of the Comparative 011 A ggf gg to g g fi i kqgle and fi ifi substltuted. g the grams of for one hour. The temperature was then slowly brought exanedlo use m Comparative rease to 350 F. and 24 grams of sorbitol, 24 grams of 1,6-hex- Comparative Grease CEifect of sorbitol 0 anediol and 200 grams of Oil A were added. The temperature was then further raised to 390 F. and 1800 Austria 225.5 .15.21; ggfiz zrssiorrziz i A 6 grams substituted for the 16 grams of 1,6-hexanediol used in ylamlfle annoxldant) were 400 grams of the Comparative Grease A resulting mixture were then placed in a mixer together Table I, which follows, summerizes the composition y f g of addltlonal 011 A to produce a and properties of the preceding greases. The percent soap 15 e gr EXAMPLE 5 and percent modifier in said table represent the approxi mate wt. percent found in the final grease composition. 562 grams of 12-hydroxy stearic acid and 1500 grams TABLE I Comparative Comparative Comparative Ex. 1 Ex. 2 grease A Ex. 3 grease B grease 0,

Percent soap 9.0 8.8 11.3 9.1 9.8 7.2 Percent sorbitol 0.12 0.12 0.06 0.12 Peroent 1,6-hexanediol- 0. 12 0. 12 0. 24 0. 06 0. 12 Dro ping point, F... 395 381 AS 1% l P-217 Penetration, mm./10 at Unwor 319 321 298 ...--.-.--.-.-z 300 304 Worked strokes (60X)-.. 316 319 322 311 306 312 Worked 10,000 strokes 327 320 310 Worked 100,000 strokes (100MX)--- 319 301 367 305 330 336 Percent A (IOOMX-fiOX strokes) +1 3.8 +14 2 +7. 8 +7. 8 ASTM D-1831-64 rou Stability, percent A in 4 hours 0. 3 9. 1 40. 0 10. 0 26. 7 20. 8

ASTM-D-217 can be used as a structural stability test 65 of Oil A were added to a laboratory grease kettle and to determine the ability of a grease to withstand prolonged were mixed at 1 0 R Then 3 5 grams f i i use under severe working conditions. The working con- 1 o sists of placing the lubricating grease in a cylinder cup droxide were added and the heat was raised to 200 and operating a perforated plate for the number of strokes and bled for one hour- The heat was then Talsed to 340 as indicated in Table I at 77 F. The percent of change F. and 8 grams of sorbitol and 8 grams of glycerol were of Penetration at strokes and at 100,000 Strokes is added. The temperature was then further raised to 380 g zasi fg gzg z thc lower the percent figure the more F. and held for 1 hour. 1000 grams of the resulting mix- The R011 Stability Test (ASTM D 1831 64) is a test ture were then placed in a Hobart mixer and 1775 grams to measure stability toward shear. The equipment conadditlonal Oil A were added.

EXAMPLE 6 562 grams of 12-hydroxy stearic acid and 1500 grams of Oil A were added to a laboratory grease kettle and mixed at 150 F. 88.5 grams of lithium hydroxide were then added and the composition was mixed to 212 F. for one hour. The temperature was then slowly brought to 350 F. and 8 grams of sorbitol, 8 grams of 1,2,6-hexanetriol and 200 grams of Oil A were added. The temperature was then further raised to 390 F. and 1800 grams additional Oil A and 6 grams phenyl alpha naphthylamine (an antioxidant) were added.

635 grams of the resulting mixture were then placed in a mixer together with 165 grams of additional Oil A to produce a grease having an ASTM worked penetration after '60 strokes of 317 mm./10.

Table 11 illustrates the excellent properties of the greases formed in these examples using various concentrations and combinations of modifiers.

30 grams of water, were then added and the heat was raised to 200 F. and held for one hour. The temperature was then raised to 370 F. and two grams of glycerol and two grams of 1,2,6-hexanetriol were added and the temperature was raised to 40 F. The heat source was removed and the mixture was allowed to cool overnight quiescently. The product, which gelled after standing overnight, was milled in a three roll paint mill together with 375 additional grams of Oil B which were added to produce a No. 1 grade grease.

EXAMPLE 9 TABLE III Example 7 Example8 Example 9 1.0 sorbitol 0.2 glycerol 0.2 sorbitol. Mmlfier Percent --i1.0 1,6hexanedio1 0.2 1,2,6-hexanetrio1 0.2 1,6 hexanedio1. Soap, percent. 11 7 7. ASTM Penetration, 77 F., mmJlO:

Unworked 295 327 Worked strokes (00X).. 300 334 are. Worked 10,000 strokes (10M) 332 360 307. Percent A(10MX60X) 10 a 3. Static hardening, percent A in 28 days:

At 77 F. 41 2s 19. At 250 49 as 27.

TABLE H The static oven hardening test is a measure of the E E E 6 35 hardening of greases due to standing for periods of time. This is an important characteristic related to their per- Percentsoap 9 g 5 formance in lubricating bearings. The test procedure con- Percent modifier 1 30:13 1 sls s essentially of initially working a grease 60 strokes Drop point, F. Ti? 382 400 383 with a penetration apparatus consisting of a modified ittitttttatnfiflf 317 an 317 cone, Such cone P 9 g p n ations about one-half Worked 10,000 strokes gag mu the scale of penetration produced by the usual cones. The g i p gg o ggggg gg a 6 +22 initially worked greases are then stored at room tempera Roll stability, percentAinihourS 14.7 9.5 ture and at a temperature of 250 F. After 1, 7 and 28 ,SorbitoL days, a penetration test using the modified cone is con- 2 lshexanedioi ducted on the stored unworked greases and the percentage 3 Glycerol. 4)

4 1,2,6-hexanetrio1.

Example 4 illustrates the elfectiveness of sorbitol and 1,6-hexanedio1 at higher concentrations and Examples 5 and 6 are illustrative of the elfectiveness of other combinations of modifiers.

An additional batch of greases was prepared to demonstrate that greases with low soap content and good-toexcellent static hardening properties could be prepared by employing a combination of modifiers.

EXAMPLE 7 75 grams of 12-hydroxy stearic acid and 600 grams of a mineral oil having a flash point of 388 F., a specific gravity of 22 API and a viscosity at 210 F. of 55 SUS (hereinafter referred to as Oil B) were blended together and heated to 160 F.; 10.5 grams of lithium hydroxide dissolved in 30 grams of water were then added. The mixture was heated to 200 F. and mixed for one hour. The temperature was then slowly increased to 360 F. Seven grams of sorbitol and seven grams of 1,6-hexanediol were mixed together and added and the temperature was raised to 400 F. The heat source was then removed and the mixture was allowed to cool quiescently overnight. The product which gelled overnight was then milled.

EXAMPLE 8 75 grams of 12-hydroxy stearic acid and 600 grams of Oil B were added to a Hobart mixer and heated to 160 F.; 10.5 grams of lithium hydroxide dissolved in of change in penetration is determined.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiments be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate the scope of the invention.

What is claimed is:

1. In a lubricating grease of the type comprising a major amount of lubricating oil and about 3 to about 25 wt. percent of a lithium soap of a C hydroxy fatty acid as a thickening agent, the improvement comprising having in admixture with said oil about .01 to about 2 wt. percent of a synergistic stability-imparting combination of two different C C aliphatic polyol modifier compounds in a relative molar ratio to each other ranging from about 4:1 to about 1:4.

2. The composition of claim 1 wherein said combination of two modifiers are C2-C10 acyclic polyols.

3. The composition of claim 1 wherein the amount of hydroxyl substitution in each of the modifiers ranges from about two to about eight hydroxyl substitutions.

4. The composition of claim 1 wherein said combination of modifiers are C -C acyclic polyols.

5. The composition of claim 1 wherein the amount of hydroxyl substitution in each of the modifiers ranges from two to six hydroxyl substitutions.

7 6. The composition of claim 1 wherein the total amount 2,606,874 8/ 1952 Garner et a1 25252 of said combination of modifiers is between about 0.1 and 2,815,560 12/ 1957 Buxton 25256 about 1 wt. percent of the total composition. 3,158,574 11/1964 Greenwood et a1. 25242 7. The composition of claim 1 wherein said combina 3,235,510 2/ 1966 Collings et a1. 25233.4 tion of modifiers is sorbitol and 1,6-hexanediol.

0 8.,The composition of claim 1 wherein said combina- DANIEL WYMAN, Primary Examine! tion of modifiers consists of two modifiers having a rela- I. VAUGHN Assistant Examiner tive molar ratio to each other ranging from about 2:1 to

about 1:2. US. Cl. X.R.

References Cited 10 25252 R UNITED STATES PATENTS 2,449,312 9/1948 Murray et a1 25242 

